Pope Benedict XVI celebrated parts of Sunday's Mass with his face looked up the East and the Cross and his back turned on the congregation, re-introducing an old ritual that had not been used in decades.
The Pope used the Sistine Chapel's ancient altar set right against the wall under Michelangelo's dramatic depiction of the Last Judgment, instead of the altar placed on a mobile platform that allowed his predecessor John Paul II to face the faithful.
A statement by the Vatican's office for liturgical celebrations said it had been decided to use the old altar, where ballots are placed during papal elections, to respect "the beauty and the harmony of this architectonic jewel."
That meant that for the first time in this kind of celebration since the Second Vatican Council (1962-65), the Pope turned his back on the faithful and faced the East and the Cross. He also read his homily from an old wooden throne on the left of the altar used by Pius IX in the 19th century.
The Pontiff is slowly reintroducing some of the old rituals phased out after Vatican II, which substituted Latin for local languages, modernized the Church and encouraged inter-religious dialogue.
In July, the Pope issued a decree allowing wider use of the old Latin Mass, in what was regarded as a nod to Church traditionalists. He has also said he would like the centuries-old Gregorian chant to make a comeback.
During Sunday's mass commemorating the baptism of Jesus Christ, which was celebrated in Italian, the Pope baptized 13 babies, carefully pouring water on their heads from a golden shell.
He spoke about the significance of baptism, which marks the admission of a person in the community of Christians.